Networks (and probably other things) are never cleaned up and docker has limits

[atamon]

I ran into the following while running build-contract locally:

Creating network "yoleanlive3yoleanliveclientunittests_default" with the default driver
ERROR: failed to parse pool request for address space "LocalDefault" pool "" subpool "": could not find an available predefined network

It seems related to moby/moby#23971 where they conclude that docker-compose down removes any created networks from the docker-compose run. Might we want to do this instead of docker-compose kill at https://github.com/Yolean/build-contract/blob/master/build-contract#L66?

[atamon]

We now do docker-compose rm -f. But #18 suggests that we actually use down as it not only helps with removing networks, but also (anonymous) volumes.